Preserve case-insensitive sorts in uv add (#7864)

## Summary

Resolves https://github.com/astral-sh/uv/issues/7801

## Test Plan

`cargo test`

crates/uv-workspace/src/pyproject_mut.rs

@@ -533,26 +533,57 @@ pub fn add_dependency(
 
     match to_replace.as_slice() {
         [] => {
+            #[derive(Debug, Copy, Clone)]
+            enum Sort {
+                /// The list is sorted in a case-sensitive manner.
+                CaseSensitive,
+                /// The list is sorted in a case-insensitive manner.
+                CaseInsensitive,
+                /// The list is unsorted.
+                Unsorted,
+            }
+
             // Determine if the dependency list is sorted prior to
             // adding the new dependency; the new dependency list
             // will be sorted only when the original list is sorted
             // so that user's custom dependency ordering is preserved.
+            //
             // Additionally, if the table is invalid (i.e. contains non-string values)
             // we still treat it as unsorted for the sake of simplicity.
-            let sorted = deps.iter().all(toml_edit::Value::is_str)
-                && deps
-                    .iter()
-                    .tuple_windows()
-                    .all(|(a, b)| a.as_str() <= b.as_str());
+            //
+            // We account for both case-sensitive and case-insensitive sorting.
+            let sort = deps
+                .iter()
+                .all(Value::is_str)
+                .then(|| {
+                    if deps.iter().tuple_windows().all(|(a, b)| {
+                        a.as_str().map(str::to_lowercase) <= b.as_str().map(str::to_lowercase)
+                    }) {
+                        Some(Sort::CaseInsensitive)
+                    } else if deps
+                        .iter()
+                        .tuple_windows()
+                        .all(|(a, b)| a.as_str() <= b.as_str())
+                    {
+                        Some(Sort::CaseSensitive)
+                    } else {
+                        None
+                    }
+                })
+                .flatten()
+                .unwrap_or(Sort::Unsorted);
 
             let req_string = req.to_string();
-            let index = if sorted {
-                deps.iter()
-                    .position(|d: &Value| d.as_str() > Some(req_string.as_str()))
-                    .unwrap_or(deps.len())
-            } else {
-                deps.len()
+            let index = match sort {
+                Sort::CaseSensitive => deps
+                    .iter()
+                    .position(|d| d.as_str() > Some(req_string.as_str())),
+                Sort::CaseInsensitive => deps.iter().position(|d| {
+                    d.as_str().map(str::to_lowercase) > Some(req_string.as_str().to_lowercase())
+                }),
+                Sort::Unsorted => None,
             };
+            let index = index.unwrap_or(deps.len());
 
             deps.insert(index, req_string);
             // `reformat_array_multiline` uses the indentation of the first dependency entry.

crates/uv/tests/edit.rs

@@ -4691,7 +4691,76 @@ fn sorted_dependencies() -> Result<()> {
         description = "Add your description here"
         requires-python = ">=3.12"
         dependencies = [
+            "anyio>=4.3.0",
             "CacheControl[filecache]>=0.14,<0.15",
+            "iniconfig",
+            "typing-extensions>=4.10.0",
+        ]
+        "###
+        );
+    });
+    Ok(())
+}
+
+/// Ensure that the added dependencies are case sensitive sorted if the dependency list was already
+/// case sensitive sorted prior to the operation.
+#[test]
+fn case_sensitive_sorted_dependencies() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+    [project]
+    name = "project"
+    version = "0.1.0"
+    description = "Add your description here"
+    requires-python = ">=3.12"
+    dependencies = [
+        "CacheControl[filecache]>=0.14,<0.15",
+        "PyYAML",
+        "iniconfig",
+    ]
+    "#})?;
+
+    uv_snapshot!(context.filters(), context.add().args(["typing-extensions", "anyio"]), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 14 packages in [TIME]
+    Prepared 13 packages in [TIME]
+    Installed 13 packages in [TIME]
+     + anyio==4.3.0
+     + cachecontrol==0.14.0
+     + certifi==2024.2.2
+     + charset-normalizer==3.3.2
+     + filelock==3.13.1
+     + idna==3.6
+     + iniconfig==2.0.0
+     + msgpack==1.0.8
+     + pyyaml==6.0.1
+     + requests==2.31.0
+     + sniffio==1.3.1
+     + typing-extensions==4.10.0
+     + urllib3==2.2.1
+    "###);
+
+    let pyproject_toml = context.read("pyproject.toml");
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            pyproject_toml, @r###"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        description = "Add your description here"
+        requires-python = ">=3.12"
+        dependencies = [
+            "CacheControl[filecache]>=0.14,<0.15",
+            "PyYAML",
             "anyio>=4.3.0",
             "iniconfig",
             "typing-extensions>=4.10.0",